Had to have a Jeep

[jweisbro]

When i parked the Jeep in the fall it ran great. When i brought it out in the spring it has a terrible miss. So I started with a new condenser, No change. Checked the fuel and cleaned the carb, no change. New coil, no change. New plug wires, rotor and cap, no change. Now it's serious. I pulled the intake/exhaust and looked for a bad valve spring, nope. Rolled the engine around to make sure the valves went up and down with lifter clearance twice. all's well there. put it all back together and NO CHANGE. The miss is still there, and it won't perform at all in 3rd gear. Second is pretty bad as well. So i checked the fuel one more time and No change.
I'm at the end of the rope and there has been no advice given that i haven't tried. It's a simple20150823_160201.jpg machine. What could I be missing? It's a CJ-3A 21734.

[bmorgil]

jw, if you are confident in the condition of the cap, rotor, points, coil, plugs and wires the next step is compression. Assuming the carburetor is ruled out as a problem, warm it up first and follow the procedure in the Universal Service Manual. Read the plugs as you pull them. You are looking for how quickly it pumps up and if there is a large difference between cylinders. Not necessarily the actual number, though a very low number is a problem. The little 134 only has 6.5 to one compression. Keep posting what you find jw, these mysterious ones are always interesting.

[jweisbro]

Yes mysterious indeed. I was really happy in how much compression it had. I could park it on an incline and the jeep would stay put. I will have to add that I did a quick valve job shortly after I brought it home, meaning I didn't replace the guides. I have the tools to cut seats and I match the valves on the lathe. Blasted the head and a new copper gasket.
it was also suggested to put air to each cylinder to see if it came out of the exhaust or intake when it shouldn't. I haven't done any of that or a compression test as i broke my arm a while back and it wasn't important. Thanks for your take and I'll try that next.
I did inspect the carb when I had everything apart and didn't find any build up and it was clean. It's a new Solex, maybe that's the problem in itself. I notice the whole assembly will come loose and fuel pours out everywhere. I need to keep that in check and tighten it up occasionally.

[gmwillys]

It's no fun having a broken limb while trying to enjoy your Jeep. When you do the compression test, you've done the work on the valve train and the head gasket, but the piston rings may be suspect. A stuck ring can cause you issues. First, as Bmorgil said, inspect your plugs to see how the cylinders are firing. Then, when you perform a compression test, do the first one dry. If the numbers are not close across the board, then perform a second round with a small amount of transmission oil to see if your pressures increase.

[jweisbro]

Ok, I did the compression test today and the results are sad. I stated that i checked the valve springs and clearance however a distinct valve tick can be heard so it's all on me for being too optimistic and not seeing anything wrong in the compartment.
The engine starts well. After running for maybe a minute or so the exhaust starts tiffing and the valve noise can be heard. I guess I'll be back into it for some R&D.
The compression test is as follows, #1, 75lbs, #2, 72lbs, #3, 65lbs, #4, 55lbs. The low readings don't bother me that much as the engine isn't using any oil and I mainly putt around the countryside with it, but I'm not going to tear it down for just a valve. At least I've had a few years trouble free.
Taking it apart will be a wonder since the last guy that tore into it brazed all the body parts together.

[bmorgil]

After 4 pumps 75# cold is not surprising on a cold or cool motor. 65# is low and that 55# number might just miss once and a while. If you had it warm, a little closer to at least 90# min would have been better. The big difference between the first cylinder and the last is also what you are looking for. That's too far apart. They need to stay within 10 psi of each other or so. That indicates a problem on the last cylinder. If its not using oil, I would say the valve seal is suspect in the last two cylinders. If the oil is getting dirty quick and its showing up on the plugs, the rings and cylinders might be getting worn.

If you have a vacuum gauge, check it at idle. You should have a good solid 17 Hg or so at idle. If the gauge is jumping 4 Hg or so, the valves are too tight or, bad.

[jweisbro]

I'm afraid it's worse than expected. Yesterday when moving it back into the shed it started blowing white smoke, anti-freeze. Well, I know what's next.
I'll keep my post open for future highlights.

[bmorgil]

Well at least we know where that compression was going!

[jweisbro]

So I pulled the head today. Looks like the gasket yielded between 3 and 4. I don't see any piston or cylinder damage, No valve damage. I do see rust around the back center studs. I'll do a bore check but ultimately I think I'll clean it up and put a new head gasket in and see how she rolls. Did I run her for a few miles and re torque the head bolts? I don't remember.Attachment 9900
Not a very clear pic.100_1059.jpg

[LarrBeard]

I would lay a straight edge across that head just to see if there is any warp to it. If there is, while it's off is the easiest time to plane it back flat.